#include <iostream>

using namespace std;
typedef long long LL;

const int N = 25;
LL f[N][N];
int x, y, n, m;

bool check(int i, int j)
{
	return (i == x && j == y) || (i != x && j != y && abs(i - x) + abs(j - y) == 3);
}

int main()
{
	cin >> n >> m >> x >> y;
	n++; m++; x++; y++;

	f[0][1] = 1;
	for(int i = 1; i <= n; i++)
	{
		for(int j = 1; j <= m; j++)
		{
			if(check(i, j)) continue;
			f[i][j] = f[i - 1][j] + f[i][j - 1];
		}
	}

	cout << f[n][m] << endl;
	
	return 0;
}

